1. Field of the Invention
The present invention relates to the identification of land vehicle license plates; and more particularly, to a license plate number recognition system mounted on a surveillance vehicle such as a police car or the like.
2. Description of the Prior Art
Identification of motor vehicles on the road is known in the art. U.S. Pat. No. 6,052,068 to Price et al. discloses a vehicle identification system for identifying one or more motor vehicles within a group of vehicles at distances in excess of 200 feet. The system requires special vehicle identification tags to be attached to the vehicles for receiving interrogation signals and sending a response signal to an interrogator. U.S. Pat. No. 4,866,438, to Knisch, discloses a traffic-monitoring device for photographically recording vehicles that exceed a predetermined speed. The vehicles are photographed frontally when they exceed the predetermined speed. The photograph is processed and inspected manually to ascertain the license plate number of the speeding vehicle.
A license plate number reader was announced in April 1994 and is available from Racal Radio Limited, Reading, England. It reads license plates from a recorded video image using recognition techniques and neural networks. The system includes a camera, lighting, plate recognition unit and keyboard and cost about 20 thousand dollars in 1994. U.S. Pat. 4,817,166, to Gonzalez, et al., discloses a device for reading a license plate. The Gonzales, et al. device uses a video camera to produce an image of a license plate on a vehicle, and a scanning means to locate a license plate number in the image. The identification of the license plate number is verified in a confidence check section by checking for the presence of a state logo. It incorporates decision means for comparing the block to second criteria to determine and indicate whether a block is an image of the license plate characters.
U.S. Pat. No. 5,381,155 to Gerber discloses a method and system of traffic control which includes the steps of measuring the speed of a vehicle, automatically reading the license plate of the vehicle, using a computer system to automatically match the license plate number with information about the owner of the vehicle, and displaying the name of the owner of the vehicle.
U.S. Pat. 6,081,206 to Kielland discloses a parking regulation enforcement system having a video camera mounted on a parking enforcement patrol vehicle and connected to a computer near the operator. The system is driven along a patrol route where parked vehicles are governed by a posted time limit. The system enforces the local parking regulation by reading license plate numbers and automatically determining whether or not each parked car has been parked longer than the posted time limit. The system makes no determination of whether the car is stolen, or if its owner is missing or wanted by the police.
Each of the above described license plate readers is completely automated. As a result, the information match must be very accurate. Information provided by the search mechanism is, of necessity, highly specific. That is to say, the image provided by the search mechanism must include substantially the entire license plate before the license plat number is interpreted. Some of the prior art systems perform additional checks, such as identifying the state logo, to improve accuracy. As a result, previous vehicle identification systems of the type described are complicated and expensive. The high degree of accuracy required of automated vehicle identification systems causes license plate numbers to be missed, oftentimes preventing proper identification of incorrect license plate numbers.
It is not unusual for a police officer in a patrol car to follow hundreds of vehicles each day in the normal course of duty. Some of these vehicles may be stolen; or the vehicle owners may be wanted by police. It is not practical for the officer to manually check all the license plates of these vehicles. Typically, the only vehicles that undergo a license plate check are those found to have violated a traffic law or which somehow arouse the suspicion of the officer.
The exists a need in the art for a vehicle identification system which (i) continually monitors the license plates of vehicles in the path of a police vehicle; (ii) automatically checks law enforcement databases to ascertain owner identification and vehicle information; and (iii) flags the record on a display if the legal status of the vehicle or its owner is the subject of an investigation. Such a system need not determine whether the character sequences it finds in an image are identical with those resident in the law enforcement database. It should be capable of withstanding occasional inaccuracies while increasing the incidence rate of potential license plate identifications, since the officer can visually verify whether the matched license plate number is correct. Also needed is a vehicle identification system that remains operable whether the surveillance vehicle, the target vehicle, or both are stationary or moving. Previous vehicle identifications systems do not fill this need.
The present invention provides a method and system for surveillance of license plate numbers from a vehicle mounted camera in situations where the surveillance vehicle and the target vehicle may both be moving. Specifically, the invention provides a license plate surveillance system having an electronic camera mounted on a surveillance vehicle for capturing an image of the license plate. A processor having an optical character recognition engine converts character sequence groups within the image to machine readable format. The processor is additionally provided with means for matching the character sequence groups with license plate numbers resident in a license plate number database. Each of the license plate numbers in the database is associated with a record that contains information about the vehicle and its owner. Matched records detected by the system are indicated on a display device disposed within the surveillance vehicle.
Alternatively, the database of license plate numbers is in a location remote from the surveillance vehicle. In this embodiment, the system further comprises a server associated with the database. Communication between the surveillance vehicle and the database is accomplished using a wireless transceiver within the surveillance vehicle for transmitting the character sequence groups to the server and receiving the associated records of matched license plate numbers. A wireless transceiver associated with the server receives the character sequence groups and sends the records of matched license plate numbers to the surveillance vehicle.
The invention also provides a method for identifying license plate numbers, using an electronic camera mounted on a surveillance vehicle. A video image is captured with the electronic camera; then any character sequence groups within the image are converted to machine readable format using a processor having an optical character recognition engine. The character sequence groups are compared with license plate numbers in the database in order to find at least one match. The record associated with a matched character sequence group is displayed on a display device in the surveillance vehicle. In this manner, a license plate number of any vehicle present within a field of view of the electronic camera is interpreted as a character sequence group. The character sequence groups found in the image are converted to machine-readable format by the optical character recognition engine and are compared with the database. Any matching license plate number and its associated record is displayed within the surveillance vehicle.
Alternatively, the database is housed in a location remote from the surveillance vehicle, and the method additionally comprises the steps of (i) sending the character sequence groups to a remote server that is associated with the database via a wireless connection, and (ii) sending the matching license plate number and its associated record via wireless connection to the surveillance vehicle.
The invention provides a method and system that searches continuously for license plate numbers without having to search for the license plate in the image. Unlike previous vehicle identification systems, no component is designated to find solely the license plate number. All character sequence groups are, instead, treated equally by the optical character recognition engine. Virtually each character sequence group in the image is treated as a possible license plate number. Identification incidence of license plate numbers is increased. The matched license plate numbers are readily verified by a system operator. Complexities inherent to previous vehicle identification systems are eliminated. The vehicle identification system remains operable whether the surveillance vehicle, the target vehicle, or both are stationary or moving.